This application directly addresses the Lupus Research Program Focus Areas: (1) understanding disease heterogeneity (how the differences in disease expression can be used to determine treatment outcomes/options), and (2) determining the pathobiology of lupus disease (how different molecules contribute to kidney disease). The most severe complication of lupus is kidney disease (nephritis), which affects up to two-thirds of lupus patients and is associated with increased complications and death. Lupus nephritis shares features with other chronic kidney diseases, including elevation of lipids called glycosphingolipids, which are important for proper function of the kidney. We demonstrated that glycosphingolipids called lactosylceramide and hexosylceramide are significantly higher in the urine of lupus nephritis patients. We also showed that the levels of these lipids in urine before beginning treatment are significantly higher in lupus nephritis patients who failed to respond to treatment compared to patients who had a complete response to treatment. Using a cutting-edge approach, we also identified several molecules called N-glycans in the urine that are either significantly higher or lower in lupus nephritis patients compared to healthy subjects or in lupus nephritis patients who failed to respond to treatment compared to patients who completely responded to treatment.

Our preliminary data is based on relatively small groups of patients (less than 30). While we observed significant differences between these small groups, analyses of additional subjects are required to confirm and validate the identification of these lipids and N-glycans as potential biomarkers. In this application, we propose to measure lactosylceramides, hexosylceramides, and N-glycans in urine samples from 130 healthy subjects, 130 lupus patients without nephritis, and 180 lupus patients with nephritis to establish a panel of biomarkers that clearly identifies: (1) kidney disease in lupus, and (2) biomarkers that are better than conventional clinical measures for predicting treatment response prior to starting treatment. Patients typically are evaluated for therapeutic response 6-12 months after starting a treatment and those that fail to respond risk developing more severe kidney disease during that time. Predicting treatment response prior to beginning treatment would allow physicians to make more informed treatment decisions and spare patients from accumulating kidney damage by using more aggressive therapies or more frequent monitoring. We will also perform studies in kidney cells using cell cultures to better understand how lactosylceramide and hexosylceramide contribute to the dysfunction of kidney cells. The cell culture studies will provide clues to the underlying reasons for kidney disease and identify potential new molecules to target as therapies to treat patients with lupus nephritis.

Using urine as a source of biomarkers is non-invasive, and the proposed measures can be performed relatively quickly. Thus, this is an attractive approach for both patient and physician to quickly inform treatment decisions with a significant, positive impact on the lupus patient population. Since we have access to urine samples from nearly 600 lupus patients, including approximately 200 lupus nephritis patients already collected and stored, we anticipate that a panel of biomarkers could be established by the end or shortly after the 3-year Department of Defense funding period. We also anticipate we will have identified new potential therapeutic targets and contributed significant knowledge of how glycosphingolipids influence kidney cell function.